The present invention pertains to motor-driven saws, particularly to a hand-held compass saw.
Compass saws in which reciprocating rods are roundshaped shafts are known. One of such saws is described in the German Patent Publication No. DE-05 30 299. In the known arrangements, the coulisse which drives the reciprocating rod connected to the saw blade is usually employed, and it is necessary to provide a guidance in the coulisse for the reciprocating rod, in order to ensure the correct position of the saw blade connected to the end of the reciprocating rod in the direction of the saw cut. Such reciprocating shafts with such guiding coulisses are relatively heavy. Furthermore, they are expensive in manufacturing because a precise adjustment of the guiding box for the reciprocating rod with the slide guide of the coulisse must be ensured. This costly manufacturing makes the compass saw even more expensive. The heavy weight of the round reciprocating rod and of the guide components of the coulisse stipulate high oscillating masses resulting in respective loads on the parts for driving and guiding the reciprocating rod.
German No. DE-GbM 77 10 558 discloses a saw with a reciprocating rod formed of a relatively flat material and installed in the assembly in the plane perpendicular to the plane of the saw blade. Such a reciprocating rod is usually formed integrally with a coulisse, which serves for its driving. In order to be able to transmit a work pressure to the saw without deforming the reciprocating rod, the latter must be very robust, e.g. sufficiently wide and thick. The saw clamping device arranged on the reciprocating rod must seize the saw blade extended perpendicularly to the plane of the reciprocating rod and therefore, should also be comparatively large and heavy and a transition from the plane of the reciprocating rod to the plane of the saw blade should be handled also. Furthermore, in these conventional arrangements, forces caused by heavy masses occur. Finally, another disadvantage of conventional compass saws resides in that the end of the reciprocating rod is exposed to the hands of the operator, which is undesired. The application of the protective shields has not been successful because the known constructions of the holders at the ends of the reciprocating rods precluded the installation of the protective shields for operation with the saw blades.